4 Answers
4

I guess the good illustration here would be to imagine the case when lets say the truck a/c malfunctions and fish is not stored at the appropriate temperature during the transportation from ship to warehouse.
If IoT sensors are offline then fish dealer might have packs of "backup" chips which could be quickly programmed to show that there was no problem with storage temperature. This "cheat" is economically beneficial since IoT sensors are cheap and reprogramming is cheap. The most difficult part is to replace the chips, but it's also not very expensive.

On the other hand if sensors are online and constantly transmitting information that would be impossible to hide the fact once it happened. And blockchain is needed to guarantee that once this even was recorded nobody would be able to modify it or make the data disappear because of some mysterious "HDD failure" or something.

The buyer could provide some key so that the data on the sensors would be encrypted and only the buyer could access the data and he/she could verify that this sensor wasn't hacked, I guess.
– DefozoOct 2 '17 at 10:00

When I wrote 'buyer' I meant the owner of the restaurant.
– DefozoOct 2 '17 at 11:42

I can see what blockchain offers but I'm not sure if it couldn't be solved in an easier way without it.
– DefozoOct 2 '17 at 11:48

You mean that store owner gives some hardware to fish distributor and it gives this hardware to fishermen which then use this hardware to encrypt each sensor? That will work but it seems quite complicated workflow: each fisherman should know beforehand who'll be the buyer of the fish and take all end clients` sensors on the ship. And then there is a need to encrypt each fish with different hardware - error-prone. With blockchain there is no need to know who'll be the buyer.
– ynameOct 2 '17 at 14:40

Though I'm curious how much these sensors cost (should be very cheap to make economic sense) and how they'll connect to the internet.
– ynameOct 2 '17 at 14:41

You could have sensors simply store data offline, and that would work, but the data could be forged and so the integrity could be compromised.

The idea behind tracking the supply chain on the blockchain is that all the data that has been added to it is completely unforgeable once added and so the integrity holds. For this use case, the idea is to be able to verify every vendor the fish went through to verify where it was sourced from, etc.

The reason blockchain is a good solution for this use case is you have many players in this space--fishing boats, transportation companies, seafood companies, restaurants, retail stores, consumers. They work with each other, but do not necessarily trust each other. A decentralized ledger (DLT) helps because it is a shared responsibility to keep the data updated and correct.